[Higashino Mikan] Lovesick Big Sister (Atsuatsu Mochimochi)

Neglected by an absent mother, young Kei depends on Amane, the doting neighbor who's been almost like a mama to him — until a fever leaves him deliriously nursing at her enormous, soft breasts and her own longing for motherhood melts into something far more indulgent. Her plump, curvy body smothers the little boy as she strokes his hardening penis and climbs on top to ride him, letting him suckle her big areolae in hopes that milk might come. Even a steamy bath afterward can't cool her devotion, with Onee-chan cradling him against her chest and his cold, conveniently, still not cured.